# NTSB CEN22LA353: Sonex Sonex, N1557S, River Falls, WI, July 29, 2022

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Class 3 · Limited · Final report
- Date: July 29, 2022, 06:52 local (11:52 UTC)
- Place: River Falls, WI
- Coordinates: 44.821644, -92.644909 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=44.8216&lon=-92.6449&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Defining event: [Enroute: Fuel exhaustion](https://openairdocs.org/ntsb-events/192)
- Highest injury: Serious injuries
- Injuries: 1 serious
- Status: Completed
- Report: Approved by Office Director
- Investigation class: Class 3
- NTSB office: Central Region
- Parties: FAA Minneapolis FSDO
- NTSB case key (mKey): 105648
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN22LA353
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/105648/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=105648
- Page: https://openairdocs.org/ntsb/CEN22LA353

## Probable cause

The pilot’s improper fuel planning, which resulted in a total loss of engine power due to fuel exhaustion.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Planning/preparation: fuel planning](https://openairdocs.org/ntsb-findings/02061030): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Hulse Steven T SONEX, 1 case](https://openairdocs.org/ntsb-findings/02061030/cases.md?model=05639IK), [All aircraft, 719 cases](https://openairdocs.org/ntsb-findings/02061030/cases.md)
- [Fluids: fuel](https://openairdocs.org/ntsb-findings/01071010): Aircraft › Fluids/misc hardware · Fluid level (probable cause); cases with it: [Hulse Steven T SONEX, 1 case](https://openairdocs.org/ntsb-findings/01071010/cases.md?model=05639IK), [All aircraft, 1,695 cases](https://openairdocs.org/ntsb-findings/01071010/cases.md)
- [Engine (reciprocating)](https://openairdocs.org/ntsb-findings/01058500): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Hulse Steven T SONEX, 1 case](https://openairdocs.org/ntsb-findings/01058500/cases.md?model=05639IK), [All aircraft, 497 cases](https://openairdocs.org/ntsb-findings/01058500/cases.md)
- [Info processing/decision: decision making/judgment](https://openairdocs.org/ntsb-findings/02041520): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Hulse Steven T SONEX, 1 case](https://openairdocs.org/ntsb-findings/02041520/cases.md?model=05639IK), [All aircraft, 3,098 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Prior to flight: Preflight or dispatch event](https://openairdocs.org/ntsb-events/030); cases with it: [Hulse Steven T SONEX, 1 case](https://openairdocs.org/ntsb-events/030/sequence.md?model=05639IK), [All aircraft, 355 cases](https://openairdocs.org/ntsb-events/030/sequence.md)
- [Enroute: Fuel exhaustion](https://openairdocs.org/ntsb-events/192) (defining event); cases with it: [Hulse Steven T SONEX, 1 case](https://openairdocs.org/ntsb-events/192/sequence.md?model=05639IK), [All aircraft, 804 cases](https://openairdocs.org/ntsb-events/192/sequence.md)
- [Enroute: Attempted remediation/recovery](https://openairdocs.org/ntsb-events/060); cases with it: [Hulse Steven T SONEX, 1 case](https://openairdocs.org/ntsb-events/060/sequence.md?model=05639IK), [All aircraft, 1,422 cases](https://openairdocs.org/ntsb-events/060/sequence.md)
- [Landing: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Hulse Steven T SONEX, 1 case](https://openairdocs.org/ntsb-events/440/sequence.md?model=05639IK), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md)
- [Landing: Collision during takeoff/land](https://openairdocs.org/ntsb-events/490); cases with it: [Hulse Steven T SONEX, 1 case](https://openairdocs.org/ntsb-events/490/sequence.md?model=05639IK), [All aircraft, 1,309 cases](https://openairdocs.org/ntsb-events/490/sequence.md)

## Analysis

The pilot completed the preflight inspection with no issues noted; the airplane had about 10.3 gallons of fuel onboard for the local flight test. The airplane departed and, after flying for between 30 and 45 minutes, the pilot decided to return to the airport. Shortly thereafter, the engine sustained a total loss of power. The pilot reported that the engine did not emit any noises, nor did he notice a drop in the engine’s rpm. The pilot tried restarting the engine three times. Although the engine would “turn over,” it would not start. The pilot elected to perform a forced landing to a corn field. During the landing, the right wing impacted a traffic sign and the airplane came to rest upright in a grass ditch. The airplane sustained substantial damage to the right wing and the fuselage. The on-site examination of the airplane found no fuel inside of the fuel tank; the fuel tank was not compromised. There were no signs of a fuel leak on the airframe or from the engine, nor were there any signs of a fuel leak or spillage on the ground at the accident site. During a postaccident examination, the fuel line to the carburetor was removed and no fuel was observed. No fuel was observed from the fuel supply line to the strainer. The bowl from the strainer was removed and no fuel was found. There were no preimpact mechanical malfunctions or failures with the airframe or the engine that would have precluded normal operation. Based on the available evidence, it is likely that the engine lost power due to fuel exhaustion.

## Factual narrative

On July 29, 2022, about 0652 central daylight time, a Sonex Aircraft Sonex airplane, N1557S, sustained substantial damage when it was involved in an accident near River Falls, Wisconsin. The pilot sustained serious injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 test flight. The pilot reported the purpose of the flight was to check the position of the trim tabs, as the right wing was “heavy,” and he would have to hold “a little left” rudder to maintain the airplane in straight-and-level flight. The pilot completed the preflight inspection with no issues noted and the airplane had about 10.3 gallons of UL94 avgas onboard for the local flight. The airplane departed from the South St. Paul Municipal Airport (SGS), South St. Paul, Minnesota. While enroute for several miles, the pilot completed the trim tab position checks and after between 30 and 45 minutes decided to return to SGS. Shortly after turning back toward the airport, at about 2,700 ft msl, the engine sustained a total loss of power. The pilot reported that the engine did not emit any noises, nor did he notice a drop in the engine’s rpm. The pilot tried restarting the engine three times. Although the engine would “turn over,” it would not start. The pilot elected to perform a forced landing to a corn field. During the landing, the right wing impacted a traffic sign and the airplane came to rest upright in a grass ditch. The airplane sustained substantial damage to the right wing and the fuselage. On-site examination of the airplane found that the sole fuel tank, located forward of the instrument panel, was intact with the fuel cap installed properly. No fuel was observed inside of the fuel tank. The fuel tank drain plug was removed, and no fuel came out. There were no signs of a fuel leak on the airframe or from the engine, nor were there any signs of a fuel leak or spillage on the ground such as with vegetation blighting at the accident site. There were no odors of fuel at the accident site. Postaccident examination of the airplane confirmed flight control continuity. Airframe to engine control continuity was established. Rotational continuity was established throughout the engine and valvetrain when the crankshaft was rotated. The fuel line to the carburetor was removed and no fuel was observed. No fuel was observed from the fuel supply line to the strainer. The drain from the fuel strainer was found separated. The bowl from the strainer was removed and no fuel was found. There were no preimpact mechanical malfunctions or failures with the airframe or the engine that would have precluded normal operation. Fuel System The Sonex Builders & Pilots Foundation has published the Sonex Aircraft New Pilot Training Guidelines and Transition Training Syllabus. This document discusses the fuel system and states: The stock fuel tank in the Sonex is a rotationally molded, polyethylene fuel cell located under the glareshield in the forward fuselage. Fuel tankcapacities vary depending on model, with the legacy Sonex models holding 16 gallons, the B-Models holding 20 gallons, and the Onex holding 15 gallons. The system is designed to operate on a gravity feed setup, and as such a fuel pump is generally not installed or needed. Fuel level monitoring can be accomplished by an electronic, capacitance style fuel probe threaded into the bottom of the fuel tank, or by incorporating a clear visual sight tube into an upper and lower port into the fuel tank. A shutoff ball-valve is standard, located under the instrument panel at the outlet of the fuel tank. It is common practice to close this valve when the aircraft is not in use.

## Aircraft

- Registration: [N1557S](https://openairdocs.org/deregistered/N1557S-2024-03-02), registration cancelled 2024-03-02, S/N 1557, built 2020 (OpenAirDocs)
- Reported make and model: SONEX AIRCRAFT SONEX (UNDESIGNATED SERIES)
- Registry model: [Hulse Steven T SONEX](https://openairdocs.org/model/hulse-steven-t-sonex) (registry code 05639IK) (OpenAirDocs)
- Registry engine: [Revmaster R-2300](https://openairdocs.org/engine/revmaster-r-2300) (registry code 52554, 4 cycle) (OpenAirDocs)
- Category: Airplane, amateur-built
- Serial number: 1557
- Year built: 2020
- Airframe hours: 18.65
- Engines: Revmaster R-2300 85 horsepower reciprocating
- Damage: Substantial damage
- Flight: Flight test, Part 91
- Airworthiness certificate: Special, Experimental (Special)
- Last inspection: Annual, October 14, 2021, 18.65 hours before
- Departed: SGS, South St. Paul, MN
- Equipment: Electronic multifunction display, ADS-B, Data recorder

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 69; injuries: serious; private; airplane ratings: single-engine land; medical: basicmed, with waivers/limitations; last flight review September 11, 2020; seat: left; restraint: 4-point; flight hours: 200 total, 15.5 in this make and model, 200 as pilot in command, 5.5 in the last 90 days, 5.5 in the last 30 days

## Weather

- Conditions: Visual (VMC), Day
- Wind: 340° at 5 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 61 °F, dew point 55 °F
- Altimeter: 30.06 inHg
- Observed at: KSGS, 17 nm away
- METAR: KSGS 291155Z AUTO 34005KT 10SM CLR 16/13 A3006 RMK AO2 T01610132 10182 20150

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 20220729013599A](https://openairdocs.org/incident/20220729013599A), Jul 29, 2022: Hulse Steven T SONEX, Prescott, WI, Substantial damage. The PIC took off from south st paul municipal airport (ksgs) at 0530 01/29/2022. The aircraft was a newly constructed experimental amateur built aircraft still…

## Docket (7 files)

The files NTSB released with the investigation on January 31, 2024, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=105648. 7.1 MB in all.

- Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 941 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16061051&FileExtension=pdf&FileName=NTSB%20Form%206120_1%20Redacted-Rel.pdf
- Accident photographs (item 2, PDF, 10 pages, 3.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16061241&FileExtension=pdf&FileName=Accident%20Photographs-Rel.pdf
- FAA aviation safety inspector - statement (item 3, PDF, 1 page, 188 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16061095&FileExtension=pdf&FileName=CEN22LA353%20-%20FAA%20ASI%20ROC-Rel.pdf
- FAA aviation safety inspector - examination report N1557S (item 4, PDF, 1 page, 50 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16061105&FileExtension=pdf&FileName=CEN22LA353%20-%20N1557S%20FAA%20Examination%20Report-Rel.pdf
- Engine data monitor - specialist factual report (item 5, PDF, 7 pages, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15766084&FileExtension=pdf&FileName=CEN22LA353%20Engine%20Data%20Monitor%20-%20Specialist%27s%20Factual%20Report-Rel.pdf
- Engine data monitor - specialist factual report - attachment 1 (item 6, CSV, 889 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15768595&FileExtension=csv&FileName=Engine%20Data%20Monitor%20-%20Specialist%20Factual%20Report%20-%20Attachment%201-Rel.csv
- Release of aircraft wreckage, NTSB form 6120.15 (item 7, PDF, 2 pages, 117 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16061199&FileExtension=pdf&FileName=NTSB%20Wreckage%20Release%20Form%20Redacted-Rel.pdf

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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